physisorption of molecules on crystalline substrates

We study diarylethene molecules (Figure) which switch between open (unconjugated) and closed (conjugated) form under UV / visible radiation and can be considered as molecular switches. The question is to understand how the phenomenon takes place in the presence of substrate and in a dense molecular environment (2D self-assembled monolayers on crystalline substrate).

We have identified the self-organization of diarylethene molecules on Au (111) in the open form and in the closed form [38].

We have highlighted the switching on/off under light irradiation and locally under an STM tip [59].

We study the chirality of self-assembly and its connection with the intermolecular interactions and substrate molecules

A. Triphénylènes on Au (111) :

We have highlighted how, in the presence of the most basic Van der Waals interactions, intrinsic chirality appears when adsorbed molecules become ordered. This occurs if the molecular size is large enough, of the order of one nanometer [58].

B. Chirality in the presence of hydrogen bonds :

We studied the structural evolution of triphenylene molecules when azobenzene are incorporated in the six chains of the molecule (Figure), in order to ask the question of the role of the presence of hydrogen bonds between neighboring molecules. We highlight how the hydrogen bonds between adjacent chains transfer their chirality to the whole molecule, then to the all ordered network, even imposing the network crystallographic orientation relative to the underlying substrate Au (111).